This invention relates to a method and means for high-speed precision powder or granular weigh filling.
The requirement for the production of large quantities of precise measured amounts of chemical materials in powdered or granular form by weight has been recognized for many years. Some systems have been developed to meet this need but due to productivity limitations and design complexity they lack economic justification. Because of this, the drug industry, for instance, utilizes volumetrically controlled fill methods as a standard. One method to resolve this was developed by Andrews U.S. Pat. No. 4,431,070, however, it is a very complex system and for the most part is unable to compete favorably with volumetric fillers. Due to economic and reliability factors, existing fill by weight systems are not capable of competing against volumetric fillers except in the most demanding applications. The difficulty with requiring numerous individual units as set forth in the aforementioned Andrews patent, is the duplication of mechanical and control functions required which results in a high level of apparatus complexity with the inherent loss of reliability and relatively high capital investment. Although the aforementioned patent advanced the prior art in weigh filling it falls short in achieving the speed and reliability necessary for the high-speed precision weigh filling.
Horii, U.S. Pat. No. 4,426,006 discloses a weigh system used to sort fruits or vegetables by passing the baskets with the fruit or vegetables over a lever balance and subsequently sorting the product. This system is not feasible to be used in a powder or granular type product as it does not allow precision weights to be maintained but merely sorts the product into various weights which is totally unacceptable.
In U.S. Pat. No. 4,605,047, Bansch, et. al. discloses a filling device for bulk material, especially liquids. This method provides little or no use for bulk granular or pellet like materials.